Prostate cancer is initially an androgen dependent disease and there is mounting evidence that the androgen receptor (AR) continues to play a role in androgen ablation resistant prostate cancer. Great strides have been made in recent years in elucidating the structure of AR, identifying candidate coregulatory proteins, and in identifying some of the genes regulated by AR. Nonetheless, our understanding of the mechanism of action of AR and our knowledge of the identity of the key genes regulated by AR to induce growth of prostate cancer cells is insufficient to provide a good basis for rational development of alternate means of blocking AR activity. Our understanding of and ability to effectively block the growth of androgen independent prostate cancer is even less well advanced. Although many candidate AR coactivators have been identified by molecular biological techniques, virtually nothing is known about their individual roles in cells, their contributions to positive and negative regulation of AR target genes and to AR dependent cell growth. Moreover, their role in androgen independent AR action has not been determined. To address these issues, we propose: Specific Aim 1: To test the hypothesis that the androgen receptor plays a key role in the growth and gene expression in some androgen independent prostate cancer cells as well as in androgen dependent prostate cancer cells and to evaluate the role of receptor coactivators in both hormone dependent and independent cell growth and gene regulation. We will selectively reduce expression of candidate coactivators and assess the effects on cell growth and target gene expression. Specific Aim 2: To identify genes regulated by androgen receptor and to test the hypothesis that coactivator requirements are target gene/promoter specific. We will utilize two approaches, Affymetrix U133A chips and a novel Protein A-AR chimera containing a TEV (tobacco etch virus) protease site linker to identify AR target genes and to evaluate the consequences of coactivator reduction on target gene expression. Specific Aim 3: To utilize chromatin immunoprecipitation (CHIP) assays to identify coregulators involved in hormone dependent and ligand independent transcriptional regulation by androgen receptors and to assess the consequences of elimination of specific coregulators on the composition of proteins associated with promoters and on the post-translational modifications of proteins associated with the promoter.